Coronary territory maps associate coronary arteries with the myocardial regions to which they provide irrigation. Such maps may be used to determine which vessels should be targeted for intervention when certain functional abnormalities are detected in the tissues of the Left Ventricle (“LV”). The functional abnormalities might include infarctions, for example.
As shown in FIG. 1, a generic American Heart Association (“AHA”) coronary territory map is indicated generally by the reference numeral 10. This mapping 10 of LV territories to coronary arteries is as prescribed by AHA. The first region 12 is fed by the Left Anterior Descending Artery (“LAD”) 22. The second region 14 is fed by the Right Coronary Artery (“RCA”) 24. The third region 16 is fed by the Left Circumflex Artery (“LCX”) 26.
The AHA published a Scientific Statement in 2002 that standardized the LV coronary territories. Unfortunately, the AHA map 10, while powerful, is not patient specific. Rather, it is an average that fails to recognize the variability between subjects. The apical region of the LV, in particular, is known to exhibit significant variability among subjects. Other variations, for example, may be due to anomalous anatomical branching or the creation of collateral vascular in compensation for a stenosis.
Generally, the success of imaging techniques such as Magnetic Resonance Imaging (“MRI”) and Positron Emission Tomography (“PET”), when used as tools for aiding revascularization planning, depends upon the accuracy of the associations between regional myocardial function or perfusion or viability and the patient's coronary anatomy. Typically, generic distribution models are used to make this association. These models are based on empirical data derived from groups of patients, from which many individual patients are known to deviate.
As an example, a recent study assessed the accuracy of a generic 17-segment LV model relating coronary anatomy with myocardial regions using monoplane coronary angiography in 135 patients. Although the distribution model showed good agreement with actual coronary anatomy on average, there was discordance in more than four segments in 27 patients (20%), and discordance in more than five segments in 13 patients (10%), eight of whom had left dominant coronary distributions where the model assumes right dominance. The clinical impact of such errors was not addressed by the study.
In addition, the present inventors have performed a study, which used co-registered MRI and Multidetector Computed Tomography (“MDCT”) images to assess the correspondence of 26 individual patients to a generic coronary distribution model. In these patients, 22 patients, or 85%, were found to be discordant in at least one segment. Overall, 76 myocardial segments out of 442 total segments, or 17% of the segments, differed from their assignment by the generic model.
Therefore, although generic distribution models can accurately represent coronary anatomy on average, they are unable to account for the potentially significant variability in coronary anatomy that can exist between different individuals.